The operation of the Fluidyne heat engine at low differential temperatures

The behavior of the Fluidyne heat engine as a pump at relatively low operating temperatures (below 350°K) is discussed, a dry air closed regenerative cycle being assumed. An approximate analytical expression is derived for the temperature difference required for the pump to perform small oscillations; viscous losses and a velocity dependent load are admitted. The case of pumping against a head is also considered. Measurements of flow and temperature of a laboratory model are given and the theory discussed in the light of these results.